KR20070021154A - 3D display using variable focusing lens - Google Patents

Abstract

The three-dimensional display apparatus includes a two-dimensional display that displays a first image and a variable focusing lens that receives light from the two-dimensional display to generate a second image. Variable focusing lenses reflect light from the two-dimensional display. The first image includes a predetermined number of first depth-specific images displayed within a unit time, and the second image includes a corresponding second depth-specific image. Each depth-specific image represents a portion of a first image having the same image depth, and the two-dimensional display displays one depth-specific image at a time. The focal length of the variable focusing lens varies depending on the depth of the image for each depth displayed. Micromirror array lenses are used as variable focusing lenses. Micromirror array lenses have sufficient speed and focusing depth range for realistic three-dimensional displays.

Description

THREE-DIMENSIONAL DISPLAY USING VARIABLE FOCUSING LENS}

The present invention relates to a three-dimensional display device and method. More specifically, the present invention relates to a three-dimensional display apparatus and method employing a variable focusing lens in combination with a two-dimensional display.

The most widely known three-dimensional display method is a binocular parallax phenomenon. This method uses the principle that the human brain perceives three-dimensional images when looking at one of two images measured at different angles with each eye. This method does not actually create three-dimensional images in space. Rather, it uses the parallax of the viewer's eyes. Therefore, this method is based on the random placement of the viewer's position, binocular disparity due to the deviation of the distance between the two eyes, convergence or divergence of light, accumulation of eye fatigue, accommodation of the lens, viewing by multiple viewers, It has the disadvantage that many factors are involved, including changes in relative position of the three-dimensional image due to movement, and these factors must be considered to provide a suitable three-dimensional display.

Holography is a three-dimensional display method that generates real images in space. Due to the technical complexity and high production costs, holography has been very limited in three-dimensional image displays.

U.S. Patent No. 4,834,512 to Austin presents a three-dimensional display having a two-dimensional display, a variable focusing lens filled with a fluid, and a display and control means for controlling the lens. Two-dimensional displays sequentially display two-dimensional images representing cross sections of subjects at different depths. The fluid-filled variable focusing lens is placed in front of the two-dimensional display and has a membrane that responds to hydraulic pressure inside the lens. Austin's display is not suitable for displaying realistic three-dimensional images because of the slow focus change rate of the fluid-filled lens.

US Patent No. 5,986,811 to Wohlstadter discloses an imaging system and method for generating three-dimensional images from two-dimensional images having a plurality of image points. The imaging system includes a micro-lens array having a variable focusing distance and means for maintaining the microlenses aligned with the image points of the two-dimensional display.

Eye fatigue, multiple viewers, the practicality of the relative distance between three-dimensional images and viewers, two-dimensional and three-dimensional compatibility or exchangeability, color representation and resolution beyond the color representation and resolution of high-definition television (HDTV), low manufacturing costs, There is a need for a new three-dimensional image display apparatus and method that can satisfy the requirements associated with an excessive amount of data.

The present invention is designed to solve the disadvantages of the prior art.

An object of the present invention is to provide a three-dimensional display device having a simple structure and at the same time a realistic image representation.

It is another object of the present invention to provide a three-dimensional display apparatus and method employing a set of depthwise images.

Another object of the present invention is to provide a three-dimensional display device capable of displaying a wide range of image depth.

In order to achieve the described object, a three-dimensional display device according to a first embodiment of the present invention, a two-dimensional display for displaying a first image and a variable focusing lens for receiving light from the two-dimensional display to form a second image ). The first image includes a first depth-specific image of a predetermined number of depths displayed within a unit time, and the second image includes a corresponding second depth-specific image. Each first depth-specific image represents a portion of a first image having the same image depth, and the two-dimensional display displays one first depth-specific image at a time. The focal length of the variable focusing lens changes according to the depth of the first depth-specific image displayed. The focusing speed of the variable focusing lens is at least equal to the product of the human eye's after-image speed and the number of depths, so that the second image appears to the viewer in three dimensions. The variable focusing lens reflects light from the two-dimensional display.

Variable focusing lenses are made of micromirror array lenses. Micromirror array lenses include a plurality of micromirrors. The micromirrors are arranged on a plane to form one or more concentric circles on the plane. In particular, micromirror array lenses form reflective Fresnel lenses. By controlling translational, rotational, or both translational and rotational motion, each micromirror is controlled to vary the focal length of the variable focusing lens.

The micromirror array lens is suitable for the three-dimensional display device of the present invention in that the speed of change of focus is fast, the amount of change in focal length is large, and a large diameter can be formed.

Because micromirror array lenses are reflective, they cannot be placed linearly with respect to two-dimensional displays and viewers. Instead, a beam splitter is placed in the optical path between the two-dimensional display and the variable focusing lens. Another method performs positioning of the variable focusing lens so that the optical path reflected by the variable focusing lens is not blocked by the two-dimensional display.

The three-dimensional display apparatus may further include an auxiliary lens having a predetermined focal length, and the second image is formed by both the variable focusing lens and the auxiliary lens. The auxiliary lens serves to change or extend the range of the variable focal length of the 3D display device or to increase the size of the image.

The present invention also provides a three-dimensional display method. The method includes displaying a first depth-specific image in two dimensions, receiving light from the displayed first depth-specific image, and focusing the light according to the depth of the first depth-specific image to display the second depth-specific image; Repeating the two steps within a unit time for a predetermined number of first depth-specific images. The first depth-specific image generates a first image, and each first depth-specific image represents a portion of the first image having the same image depth. The displayed second depth-specific images produce a second image that is perceived in three dimensions by the viewer.

The focusing speed in the step of displaying the second depth-specific image is equal to at least the product of the afterimage of the human eye and the number of depths. In the displaying of the second depth-specific image, light received from the displayed first depth-specific image is reflected.

The displaying of the second depth-specific image is performed with a micromirror array lens.

In the second embodiment, the two-dimensional display apparatus includes many pixels, and the variable focusing lens includes many variable focusing lenses. Each variable focusing lens corresponds to each pixel. The focal length of each variable focusing lens varies with the image depth of the image displayed by each pixel. Each variable focusing lens is made of a micromirror array lens. The focusing speed of the variable focusing lens is at least equal to the afterimage speed of the human eye, and each variable focusing lens reflects light from the two-dimensional display device.

In both embodiments, the focal length of the variable focusing lens may be controlled so that the three-dimensional display device can be used as a two-dimensional display device. By fixing the focal length of the variable focusing lens and by means of a two-dimensional display displaying a general two-dimensional image, it is easy to switch the three-dimensional display device between the two-dimensional display and the three-dimensional display.

Advantages of the present invention are: (1) Since the three-dimensional display device actually generates a three-dimensional image in space, the device is capable of: binocular disparity, convergence or divergence of light due to arbitrary arrangement of the viewer's position, and deviation of distance between the two eyes. Does not experience the shortcomings of prior art devices using parallax with difficulty in imaging due to the consideration of the perspective adjustment of the lens, the viewing by multiple viewers, and the change in relative position of the three-dimensional image due to the viewer's movement, (2) the data requires only depth information in addition to the two-dimensional image information, so that the cost for providing three-dimensional image data is inexpensive, so that there is no significant increase in the amount of data, and (3) the apparatus can easily be used as a two-dimensional display or It can be reversed.

While the invention has been briefly summarized, the invention can be fully understood by the following figures, detailed description and appended claims.

These and other features, aspects, and advantages of this invention may be better understood with reference to the accompanying drawings.

1A-1D are schematic diagrams showing how the depth of an image changes as the focal length of the lens changes.

2 is a schematic view showing a three-dimensional display device of the present invention.

3A-3C are schematic diagrams illustrating display and focusing of images by depth.

4A is a schematic diagram showing how a refractive Fresnel lens replaces a conventional monolithic lens.

4B is a schematic diagram illustrating how reflective Fresnel lenses replace conventional monolithic mirrors.

5A is a schematic plan view showing a variable focusing lens made of multiple micromirrors.

5B is an enlarged detailed top view of the micromirror.

6 is a schematic diagram showing a beam splitter and an auxiliary lens added to a three-dimensional display device.

7 is a schematic diagram showing an enlarged lens added to a three-dimensional display device.

8A is a schematic diagram illustrating a three-dimensional display apparatus having a variable focusing lens corresponding to pixels of a two-dimensional display.

FIG. 8B is a schematic diagram showing that a micromirror array lens is employed as the variable focusing lens for the apparatus of FIG. 8A. FIG.

9 is a flowchart illustrating a three-dimensional display method of the present invention.

Detailed description of the invention

1A-1D illustrate a general principle regarding the distance or depth of an image produced by the lens and the focal length of the lens. When light from the subject passes through the lens, the light converges or diverges according to the distance L between the subject and the lens and the focal length of the lens. In the description of the present invention, a lens means an optical element that focuses light, and is not limited to only a refractive lens.

FIG. 1A shows that light from the subject 1A passes through the lens 2A and diverges at different angles. 1B is a similar view for lens 2B with a shorter focal length. The light refracted by the lenses 2A and 2B forms the virtual images 3A and 3B. When the viewer 4 sees the refracted light, the viewer perceives that the subjects 1A and 1B located at point P are at points Q and Q '.

FIG. 1C shows that light from the subject 1C converges through the lens 2C and forms a real image 3C. 1D is a similar view for a lens 2D with a shorter focal length. When the viewer 4 sees the subjects 1C and 1D through the lenses 2C and 2D, the viewer perceives the subjects 1C and 1D as actual images 3C and 3D.

Given the distance L between the subject and the lens, the position of the image formed by the lens changes with the focal length of the lens. The position of the image can be calculated by Gauss' Lens Formula. 1A and 1B show a virtual image 3A closer to the viewer 4 with a lens 2A having a longer focal length and farther from the viewer 4 with a lens 2B having a shorter focal length. Creating a virtual image 3B is shown. 1C and 1D show an image 3C closer to the viewer 4 with the lens 2C having a longer focal length, and an image farther from the viewer 4 with the lens 2D having a shorter focal length. Shows generating (3D).

1A-1D show that the position of the virtual image or the actual image changes according to the focal length of the lens, and the position of the image also changes continuously as the focal length continuously changes.

2 schematically illustrates a three-dimensional display apparatus 100 according to a first embodiment of the present invention. The three-dimensional display apparatus 100 includes a two-dimensional display 10 displaying a first image 6 and a variable focusing lens 7 receiving light from the two-dimensional display 10 to generate a second image 5. . The focal length of the variable focusing lens 7 is changed such that the second image 5 is perceived three-dimensionally by the viewer 8 of the three-dimensional display apparatus 100.

Three-dimensional images are generated in space by imaging two-dimensional images by depth at corresponding depths in space using a variable focusing lens. The two-dimensional display only displays pixels that should be imaged at the same depth at a given moment or in a given frame, and the focal length of the variable focusing lens is adjusted to image the depth-by-depth image at the required location in space.

3A-3C show a first image 6 comprising a predetermined number of depth-first images 9A, 9B and 9C displayed in unit time, and corresponding second depth-specific images 11A, 11B, A second image 5 is shown including 11C). Each first depth-specific image 9A, 9B, 9C represents a portion of the first image 6 having the same image depth. The two-dimensional display 10 displays one first depth-specific image at a time. The focal length of the variable focusing lens 7 changes according to the depth of the first depth-specific image being displayed. In order for the second image to be perceived three-dimensionally by the viewer, the focusing speed of the variable focusing lens 7 is at least equal to the product of the afterimage of the human eye and the number of depths. The variable focusing lens reflects light from the two-dimensional display.

In order for the sequentially displayed second depth-specific images to be perceived by the viewer 8 as a three-dimensional second image 5, the second depth-specific images must be displayed quickly enough to take advantage of the afterimage effect of the human eye. In other words, the variable focusing lens 7 should be able to change its focal length fast enough.

In one example, a residual image speed of about 30 Hz is required to display a three-dimensional image. In order to display a three-dimensional image with ten image depths, the ten depths must all be displayed within one-third of a second, so that the variable focusing speed and the two-dimensional display speed must be at least about 300 Hz (30 x 10 Hz).

The number of image depths varies with the structure and performance of the three-dimensional display device and is increased for better image quality.

The variable focusing lens 7 is composed of a micromirror array lens. The micromirror array lens is synchronized with the two-dimensional display 10 to display the second depth-specific images 11A, 11B and 11C according to the depths of the first depth-specific images 9A, 9B and 9C. In order to display the second image 5 having a continuous depth, the focal length of the micromirror array lens is continuously changed in synchronization with the depths of the first depth-specific images 9A, 9B and 9C. In order for the second image 5 composed of the second depth-specific images 11A, 11B, and 11C having continuous depths to be displayed in a realistic manner, the focal length change rate of the micromirror array lens and the display speed of the two-dimensional display 10 are shown. Is equal to or greater than the product of the afterimage rate of the human eye (about 30 Hz) and the number of depths of the image for each depth.

4A schematically shows how the refractive Fresnel lens 13A replaces the conventional monolithic lens 3. 4B shows how to form a reflective Fresnel lens 13B in place of a conventional monolithic mirror 12 using a micromirror array lens. The micromirror array lens includes a plurality of micromirrors 14, each micromirror 14 being controlled to form a reflective Fresnel lens 13B and vary the focal length of the variable focusing lens 7. .

In order to obtain a bright and clear image, all rays leaving a point of the subject must converge with the same phase at a point on the image plane. Therefore, the role of the lens is to converge the light rays diffused from the subject and make each light ray have the same optical path length (OPL). Alternatively, imaging employing a Fresnel lens can be achieved by giving the same period of phase to each ray by adjusting the difference of the OPLs to be an integer multiple of the wavelength [lambda], even if the rays have different OPLs. Each side converges the rays to a point, and the rays refracted or reflected from the different sides have an OPL difference of an integer multiple of the wavelength [lambda].

To change the focal length of the micromirror array lens, the translational or rotational motion of each micromirror is controlled. Another way is that both the translational and rotational movements of each micromirror are controlled. The rotational movement of the micromirror 14 serves to change the direction of light, and the translational movement of the micromirror 14 serves to adjust the phase of the light.

5A and 5B show that the micromirror 14 is arranged to form many concentric circles. The micromirror 14 is arranged in a plane as shown in FIG. 4B.

The variable focusing lens 7 must satisfy the following requirements. First, the variable focusing lens must be fast enough to change the focal length for three-dimensional display. Second, since the depth range that can be imaged depends on the variation range of numerical aperture, the variable focusing lens must have a large variation range of numerical aperture. Third, the variable focusing lens needs to have a large diameter depending on the configuration of the three-dimensional display.

Micromirror array lenses meet the above three requirements. First, the response speed of the micromirror 14 exceeds 10 KHz. Therefore, the focal length change rate of the micromirror 14 can be made equal to or greater than 10 KHz.

Second, the numerical aperture variation of the micromirror array lens is large. Therefore, as described above, micromirror array lenses have a large image depth range that is a requirement in three-dimensional displays. For example, when a 19-inch three-dimensional television is made of a micromirror array lens, it can display an image depth from 1 m to infinity.

Third, unlike lenses with continuous shapes where it is difficult to create an ideal curved surface as the size increases, it is difficult to increase the size of the micromirror array lens because the micromirror array lens is composed of discrete micromirrors. There is no

Since the micromirror array lens is a reflective lens, the optical system of the three-dimensional display device 100 cannot be aligned in a straight line. There is a need for an optical arrangement to ensure that the reflected light is not blocked by the two-dimensional display.

6 shows an arrangement of a three-dimensional display apparatus 100 further comprising a beam splitter 17 disposed in an optical path between the two-dimensional display 15 and the variable focusing lens 16. The two-dimensional display 15 and the variable focusing lens 16 are arranged parallel to each other. The beam splitter 17 changes the direction of light by 90 to simulate a straight line arrangement. The micromirror array lens is positioned perpendicular to the light path.

Another method, again referring to FIG. 2, is to position the variable focusing lens 7 so that the light path reflected by the variable focusing lens 7 is not blocked by the two-dimensional display 10. The arrangement of FIG. 2 has the advantage of having a wider field of view because its structure is simple and the distance between the two-dimensional display and the variable focusing lens 7 is closer than the arrangement using the beam splitter 17. However, there is a disadvantage that the image quality is reduced due to the aberration caused by the obliquely positioned variable focusing lens 7. Which arrangement to use depends on how the display device is used.

As shown in FIG. 6, the 3D display apparatus 100 may further include an auxiliary lens 18 positioned near the variable focusing lens 16 and having a predetermined focal length. The second image 5 is formed by the effective focal lengths of the variable focusing lens 16 and the auxiliary lens 18. By employing the auxiliary lens 18, the range of the variable focusing of the three-dimensional display apparatus 100 can be increased or changed to the required range. The auxiliary lens 18 may be a refractive Fresnel lens.

As shown in Figs. 2 and 6, the variable focusing lenses 7 and 16 should have an image size. For devices with large display images, it is almost impossible or expensive to make a variable focusing lens as large as the image. FIG. 7 illustrates that the three-dimensional display apparatus 100 may further include an auxiliary lens 21 for enlarging the second image 5 to overcome this limitation. The auxiliary lens 21 may be a general refractive lens or a refractive Fresnel lens. The size of the auxiliary lens 21 having a fixed focal length becomes the size of the screen. The size of the two-dimensional display 20 and the variable focusing lens 19 is small, much smaller than the size of the auxiliary lens 21. By changing the focal length of the variable focusing lens 19, the effective focal length of the three-dimensional display apparatus 100 is changed.

The focal length of the variable focusing lens 7 may be adjusted to be fixed. By fixing the focal length of the variable focusing lens 7 and operating the two-dimensional display 10 as a general two-dimensional display device, the three-dimensional display device 100 can be easily converted to a two-dimensional display device.

The method of displaying a three-dimensional image may be to use a virtual image as described in FIGS. 1A and 1B or may use a real image as described in FIGS. 1C and 1D. The method using the reality has the advantage that a more realistic display is possible because the image is generated closer to the viewer, but the display range is limited between the viewer and the screen. In the method of using a virtual image, an image is generated behind the screen. This method has the advantage that it can display an image having a depth range from the screen to infinity.

8A and 8B show a second embodiment of the present invention. FIG. 8A shows how a three-dimensional display device having a variable focusing lens 23 corresponding to the pixel 26 of the two-dimensional display 22 operates to display the three-dimensional image 24. The partial image displayed by each pixel 26 is imaged at image depth by the variable focusing lens 23 corresponding to the pixel 26. Since the partial images displayed by each pixel are handled separately by corresponding variable focusing lenses, it is unnecessary to divide the image into depth-specific images and display the depth-specific images. No variable focusing lens is required. Two-dimensional displays with normal speeds can be used. The size of the variable focusing lens 23 is similar to the size of the pixel 26.

8B schematically shows a three-dimensional display apparatus 200. The three-dimensional display apparatus 200 includes a two-dimensional display having a plurality of pixels 26 and a plurality of variable focusing lenses 25. Each variable focusing lens 25 corresponds to each pixel 26. The focusing speed of the variable focusing lens 25 is at least equal to the afterimage speed of the human eye, and each variable focusing lens 25 reflects light from the two-dimensional display. The focal length of each variable focusing lens 25 varies depending on the image depth of the image displayed by each pixel 26. Each of the variable focusing lenses 25 is formed of a micromirror array lens.

Since the micromirror array lens is a reflective optical element, the lens element 25 is arranged so that the reflected light is not blocked by the two-dimensional display. Each pixel 26 displays a portion of the first image in a direction perpendicular to the device display direction 27 of the three-dimensional display apparatus 200. Each lens element 25 is disposed at an angle of 45 ° with respect to the display direction of the pixel 26 and the device display direction 27. The second image 24 in three dimensions is formed by the lens element 25. Despite this complex arrangement, micromirror array lenses are used because of the large range of numerical changes of the micromirror array lenses.

9 shows a three-dimensional display method according to the present invention. In step S100, the first depth-specific image is displayed in two dimensions. In operation S200, the second depth-specific image is displayed by receiving light from the displayed first depth-specific image and focusing the light according to the depth of the first depth-specific image. In step S300, steps S100 and S200 are repeated within a unit time for a predetermined number of first depth-specific images. The predetermined number of first depth-specific images form a first image, and each first depth-specific image represents a portion of the first image having the same image depth. The displayed second depth-specific images form a second image that appears to the viewer in three dimensions. The focusing speed in the step of displaying the second depth-specific image is equal to at least the product of the afterimage of the human eye and the number of depths. In the displaying of the second depth-specific image, light received from the displayed first depth-specific image is reflected.

The step S200 of displaying the second depth-specific image is performed by the micromirror array lens.

While the invention has been shown and described with reference to different embodiments, it will be apparent to those skilled in the art that changes may be made in form, detail, configuration and operation without departing from the spirit and scope of the invention as defined by the appended claims. Will understand.

Claims (21)

a) two-dimensional display for displaying a first image; And b) a variable focusing lens that receives light from the two-dimensional display to form a second image Wherein the first image comprises a first depth-by-depth image of a predetermined number of depths displayed within a unit time, the second image comprises a corresponding second depth-specific image, and the first image Each depth-specific image represents a portion of the first image having the same image depth, the two-dimensional display displays one first depth-specific image at a time, and the focal length of the variable focusing lens is displayed on the first The depth of image varies by depth, the focusing speed of the variable focusing lens is at least equal to the product of the residual speed of the human eye and the number of depths, and the variable focusing lens reflects light from the two-dimensional display. Device. The three-dimensional display apparatus of claim 1, wherein the variable focusing lens is made of a micromirror array lens. The 3D display apparatus of claim 2, wherein the variable focusing lens is a reflective Fresnel lens. 3. The three-dimensional display device of claim 2, wherein the micromirror array lens comprises a plurality of micromirrors, each micromirror being controlled to vary a focal length of the variable focusing lens. The three-dimensional display device of claim 4, wherein the micromirror is disposed on a plane. The three-dimensional display device of claim 5, wherein the micromirror is arranged to form one or more concentric circles. The three-dimensional display device of claim 4, wherein the translation of each of the micromirrors is controlled. The three-dimensional display device of claim 4, wherein the rotational motion of each of the micromirrors is controlled. The 3D display apparatus according to claim 4, wherein the rotational motion and the translational motion of each of the micromirrors are controlled. The apparatus of claim 1, further comprising a beam splitter positioned in an optical path between the two-dimensional display and the variable focusing lens. The apparatus of claim 1, wherein the variable focusing lens is positioned such that the optical path reflected by the variable focusing lens is not blocked by the two-dimensional display. The 3D display apparatus of claim 1, further comprising an auxiliary lens having a predetermined focal length, wherein the variable focusing lens and the auxiliary lens are used together to form the second image. The 3D display apparatus of claim 12, further comprising a screen to display the second image, wherein the auxiliary lens increases the size of the screen. The 3D display apparatus of claim 1, wherein the focal length of the variable focusing lens is controlled to be fixed. The image of the subject is divided into cross-sectional images along the depth of the subject, and each cross-sectional image is focused at the depth of the cross-sectional image so that the focused image from each cross-sectional image is viewed in three dimensions by the viewer. as, a two-dimensional display for displaying a first depth image of a predetermined depth number; And b) a variable focusing lens that receives light from the two-dimensional display to form a second image Wherein the focusing speed of the variable focusing lens is at least equal to the product of the residual speed of the human eye and the number of depths, and the variable focusing lens reflects light from the two-dimensional display. 16. The method of claim 15, wherein the variable focusing lens is made of a micromirror array lens, the micromirror array lens comprises a plurality of micromirrors, each micromirror controlled to vary the focal length of the variable focusing lens. 3D display device. The 3D display apparatus of claim 16, wherein the variable focusing lens is a reflective Fresnel lens. a) displaying the first depth-specific image in two dimensions; b) receiving light from the displayed first depth-specific image and displaying a second depth-specific image by focusing light according to the depth of the first depth-specific image; And c) repeating steps a) and b) within a unit time for the first depth-specific image of a predetermined depth number; Wherein the predetermined number of first depth-specific images form a first image, wherein each of the first depth-specific images represents a portion of the first image having the same image depth, and wherein the second depth-specific images The focusing speed in the step of displaying is equal to at least the product of the residual speed of the human eye and the number of depths, and in the step of displaying the second depth-specific image, the light received from the displayed first depth-specific image is reflected. Three-dimensional display method. 19. The method of claim 18, wherein displaying the second depth-specific image is performed by a micromirror array lens. a) a two-dimensional display comprising a plurality of pixels; And b) a plurality of variable focusing lenses corresponding to each of the pixels Wherein the focusing speed of the variable focusing lens is at least equal to the residual speed of the human eye, wherein each of the variable focusing lenses reflects light from the two-dimensional display, and a focal length of each of the variable focusing lenses is defined by each of the pixels. 3D display device that changes depending on the image depth of the image being displayed. 21. The three-dimensional display device of claim 20, wherein each of the variable focusing lenses is made of a micromirror array lens.

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